There have been various proposals in the prior art for the facilitation of steering vehicles around obstacles or in close quarters where it is difficult to maneuver. It is typical of this art to provide all wheel steering in either three or four wheel vehicles, with four wheel vehicles being preferred for stability and balance in such applications as wheelchairs, lawnmowers and warehouse utility vehicles. The all wheel steering feature provides a much smaller turning radius than conventional steering from two front wheels. However any vehicle that must be backed up while steering has a significant disadvantage in that considerable driving skill is required for maneuverability. It is particularly dangerous for unskilled, untrained persons or those with limited coordination such as handicapped persons in wheelchairs to have to drive in reverse. Typically, the driving public is unable to skillfully back up to parallel park in a tight space, for example.
Furthermore even all wheel steered vehicles are inadequate for several types of circumstances that may be encountered, such as with a warehouse utility vehicle that needs to service a narrow aisle where there is no room to back up and turn around. It is always dangerous to drive a vehicle in reverse because the operator cannot have full vision or awareness of the dangers in the travel path. The all wheel steering type of vehicle is similar to conventional steering in that the wheels are turned while the vehicle is moving either forward or reverse. Thus maneuvering in confined spaces constitutes an awkward and tedious jig-jog action for inching a vehicle back and forth into an opposite travel direction.
Typical examples in the vehicle prior art for steering improvements may be found in the following U.S. Pat. Nos.: Samejima, et al., 4,977,733, Dec. 18, 1990; McClarnon, 3,110,352, Nov. 12, 1963; Mullet, 5,090,512, Feb. 25, 1992; Fry, 4,852,679, Aug. 1, 1989; Noda, et al., 4,483,405, Nov. 20, 1984; Lin, 4,664,213, May 12, 1987; Butler, 5,259,475, Nov. 9, 1993; and Roberts, 5,139,279, Aug. 18, 1992.
This invention has the general objective of overcoming deficiencies in steering methods and controls found in the prior art. In particular it is an objective to eliminate those complexities, problems and expenses introduced by mechanical steering linkages accentuating the safety problems encountered when an operator must divert attention unnaturally to the rear of the vehicle in order to drive in reverse.
Further deficiencies are exhibited in this exemplary prior art, including complex and expensive steering mechanisms and systems that are subject to failure, unreliability, high initial cost, critical operating conditions, limited scope of utility and difficulties in maintenance.
Thus, it is a further objective of this invention to provide simple, inexpensive and reliable steering and drive mechanisms for powered utility vehicles adaptable for use in a variety of applications.
Lawnmowing equipment is particularly sensitive to critical operating conditions where grass should be cut evenly without wheel scars or scalping from unbalanced cutter blade sometimes encountered in turnarounds. In common with wheelchair applications, operators riding on the vehicles are endangered if ridden vehicles are unstable and subject to tipping or collision even in the presence of uneven riding surfaces. Lawnmowers are significantly critical since turnaround locations are often encountered at the end of cutting rows near an abutment which are to be avoided, and must be steered around obstacles in their path such as trees.
It is therefore a more specific objective of this invention to produce a riding lawnmowers with simplified construction and superior performance.